Device and method for measuring repeated positioning precision of robotic arm

Abstract

A device for measuring repeated positioning precision of a robotic arm is introduced. Using an optical speckle three-dimensional displacement sensor developed by the inventor, and with collaboration of an optical speckle image three-dimensional positioning base built with an optical speckle coordinate database and having low thermal expansion, an optical speckle three-dimensional absolute positioning space is established. The optical speckle three-dimensional displacement sensor is installed on an end effector of a robotic arm, the robotic arm is moved to have the optical speckle three-dimensional displacement sensor enter an optical speckle three-dimensional absolute positioning space, an optical speckle image of a positioning point is captured and compared with a coordinate optical speckle image in the optical speckle coordinate database, and current three-dimensional absolute positioning coordinates of the end effector of the robotic arm can be obtained.

What is claimed is: 
     
       1. A device for measuring repeated positioning precision of a robotic arm, the device comprising:
 an optical speckle three-dimensional displacement sensor, having two image invariant optical speckle capturing devices perpendicular to each other and a laser displacement sensor; 
 a two-dimensional laser interferometer calibration platform, having an optical speckle image three-dimensional positioning base and the optical speckle three-dimensional displacement sensor, the optical speckle three-dimensional displacement sensor configured to emit three laser beams striking on a same position of the optical speckle image three-dimensional positioning base to capture two optical speckle images and a height value of the position, and to build, from the two optical speckle images and the height value respectively corresponding to a plurality of positions of the optical speckle image three-dimensional positioning base stricken by the three laser beams of the optical speckle three-dimensional displacement sensor, an optical speckle coordinate database having two coordinate optical speckle images and a set of three-dimensional positioning coordinates; 
 a robotic arm repeated positioning precision test platform, formed by three of the optical speckle image three-dimensional positioning bases perpendicular to one another, wherein each of the optical speckle image three-dimensional positioning bases is built with the optical speckle coordinate database; and 
 a robotic arm, comprising an end effector, the end effector installed with the optical speckle three-dimensional displacement sensor; 
 wherein, the robotic arm is moved to have the optical speckle three-dimensional displacement sensor enter an optical speckle three-dimensional absolute positioning space of the robotic arm repeated positioning precision test platform to capture an optical speckle image of a positioning point, the optical speckle image is compared with the coordinate optical speckle image in the optical speckle coordinate database to obtain X-axis and Y-axis relative displacement amounts of the positioning point relative to the coordinate optical speckle image, and further in conjunction with a Z-axis height parameter of the optical speckle three-dimensional displacement sensor and the three-dimensional positioning coordinates of the coordinate optical speckle image, current three-dimensional absolute positioning coordinates of the end effector of the robotic arm are obtained. 
 
     
     
       2. The device for measuring repeated positioning precision of a robotic arm according to  claim 1 , wherein each of the image invariant optical speckle capturing devices comprises an X-axis displacement sensor and a Y-axis displacement sensor, the X-axis displacement sensor measures a displacement amount in an X-axis direction for any point on an object surface, and the Y-axis displacement sensor measures a displacement amount in a Y-axis direction for any point on an object surface. 
     
     
       3. The device for measuring repeated positioning precision of a robotic arm according to  claim 2 , wherein the laser displacement sensor is a Z-axis displacement sensor, and comprises a laser confocal displacement sensor, a color confocal displacement sensor, a white light interference displacement sensor or a triangular measurement laser displacement sensor. 
     
     
       4. The device for measuring repeated positioning precision of a robotic arm according to  claim 3 , wherein all detection laser beams of the X-axis displacement sensor, the Y-axis displacement sensor and the Z-axis displacement sensor strike on a same point on a surface of the optical speckle image three-dimensional positioning base, operating wavelengths of the individual laser beams differ by at least 10 nm, and a ±5 nm interferometric filter is placed in front of a receiving lens of each of the displacement sensors to filter out scattered light of the remaining two laser beams so that the three laser beams do not interfere one another. 
     
     
       5. The device for measuring repeated positioning precision of a robotic arm according to  claim 1 , wherein the optical speckle three-dimensional absolute positioning space is above the optical speckle image three-dimensional positioning base, and in a three-dimensional space within a measurement height of the optical speckle three-dimensional displacement sensor. 
     
     
       6. The device for measuring repeated positioning precision of a robotic arm according to  claim 1 , wherein the optical speckle three-dimensional displacement sensor continuously captures images at a frequency of more than 10 kHz. 
     
     
       7. A method for measuring repeated positioning precision of a robotic arm, the method comprising:
 (A) establishing a two-dimensional laser interferometer calibration platform, emitting three laser beams by an optical speckle three-dimensional displacement sensor to strike on a same position of an optical speckle image three-dimensional positioning base to capture two optical speckle images and a height value of the position, and building, from the two optical speckle images and the height value respectively corresponding to a plurality of positions of the optical speckle image three-dimensional positioning base stricken by the three laser beams of the optical speckle three-dimensional displacement sensor, an optical speckle coordinate database having two coordinate optical speckle images and a set of three-dimensional positioning coordinates; 
 (B) establishing a robotic arm repeated positioning precision test platform by means of forming the robotic arm repeated positioning precision test platform by three of the optical speckle image three-dimensional positioning bases perpendicular to one another, wherein each of the optical speckle image three-dimensional positioning bases is built with the optical speckle coordinate database; 
 (C) installing the optical speckle three-dimensional displacement sensor on an end effector of the robotic arm; and 
 (D) moving the robotic arm to have the optical speckle three-dimensional displacement sensor enter an optical speckle three-dimensional absolute positioning space of the robotic arm repeated positioning precision test platform to capture an optical speckle image of a positioning point, comparing the optical speckle image with the coordinate optical speckle image in the optical speckle coordinate database to obtain X-axis and Y-axis relative displacement amounts of the positioning point relative to the coordinate image, and further in conjunction with a Z-axis height parameter of the optical speckle three-dimensional displacement sensor and the three-dimensional positioning coordinates of the coordinate optical speckle image, obtaining current three-dimensional absolute positioning coordinates of the end effector of the robotic arm. 
 
     
     
       8. The method for measuring repeated positioning precision of a robotic arm according to  claim 7 , wherein the optical speckle three-dimensional displacement sensor comprises two image invariant optical speckle capturing devices perpendicular to each other and a laser displacement sensor, each of the image invariant optical speckle capturing devices comprises an X-axis displacement sensor and a Y-axis displacement sensor, the X-axis displacement sensor measures a displacement amount in an X-axis direction for any point on an object surface, and the Y-axis displacement sensor measures a displacement amount in a Y-axis direction for any point on an object surface. 
     
     
       9. The method for measuring repeated positioning precision of a robotic arm according to  claim 8 , wherein the laser displacement sensor is a Z-axis displacement sensor, and comprises a laser confocal displacement sensor, a color confocal displacement sensor, a white light interference displacement sensor or a triangular measurement laser displacement sensor. 
     
     
       10. The method for measuring repeated positioning precision of a robotic arm according to  claim 9 , wherein all detection laser beams of the X-axis displacement sensor, the Y-axis displacement sensor and the Z-axis displacement sensor strike on a same point on a surface of the optical speckle image three-dimensional positioning base, operating wavelengths of the individual laser beams differ by at least 10 nm, and a ±5 nm interferometric filter is placed in front of a receiving lens of each of the displacement sensors to filter out scattered light of the remaining two laser beams so that the three laser beams do not interfere one another.